This Core has been an integral part of the Program Project since its inception. It will continue to provide investigators with cytogenetic documentation of DS whenever this information is not available in the medical records of the participant. In addition, it will continue to provide Apolipoprotein E (APOE) genotyping and will maintain archives of DNA as well as frozen buffy coat cells and immortalized lymphoblastoid cell lines. Together with the detailed characterization of these people provided by other Program components, these resources will be of great value for our current and future investigations as new biomarkers are identified as possible diagnostic indicators or risk factors. For example, when feasible, some of the buffy coat samples have been provided to determine whether telomere shortening may serve as a biomarker of mild cognitive impairment/dementia status in DS.